How Everything Works
How Everything Works How Everything Works

Question 1166

You stated that thermodynamics overwhelms just about everything sooner or later. Could you explain why? — MT, San Antonio, Texas
Thermodynamics is a statistical science that deals with systems that are so complicated or vast that they can't be followed in complete detail. It makes predictions of behavior based on probability theory and while some of its laws predict probable outcomes rather than certain outcomes, a sufficiently probably event is effectively a certain event. For example, I can say with near certainty that if you play the lottery 50 times, you won't win the jackpot 50 times. I can't be truly certain of that fact, but the likelihood of my prediction being correct is pretty good.

In a sense, probability is destiny. Thermodynamics observes that vast systems tend to evolve toward the mostly likely configurations. To understand this process, consider what happens when you mix hot and cold water. The most likely final configuration for the mixed water is for it to reach a uniform temperature about half way in between the two original temperatures. While it's possible for the water to end up extremely hot in one place and extremely cold in another, that outcome is extremely unlikely. It's so unlikely that it never happens.

So in what sense does thermodynamics overwhelm things? The world is filled with relatively ordered arrangements and these ordered arrangements are unlikely by themselves (how they came to be ordered in the first place is another matter for another questions). If you take a crystal vase and drop it on the floor, it's going to evolve toward a more likely arrangement of atoms and dropping it a second time isn't going to return it toward its original unlikely state. In short, ordered systems naturally drift toward disorder when given a chance. How quickly they drift depends on their situation. A coffee cup will remain a nicely ordered object for thousands or millions of years if you don't disturb it. But in a hot environment, or one that is chemically aggressive, it may not last very long.

One last thought: how do living organisms maintain their order in the face of this tendency to disorder? They do it by consuming order and exporting disorder—they eat ordered foods and release disordered wastes to their surroundings.


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